PMID:1988436
| Citation |
Stover, P and Schirch, V (1991) 5-Formyltetrahydrofolate polyglutamates are slow tight binding inhibitors of serine hydroxymethyltransferase. J. Biol. Chem. 266:1543-50 |
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| Abstract |
The interaction of the mono- and triglutamate forms of 5-methyltetrahydrofolate and 5-formyltetrahydrofolate with serine hydroxymethyltransferase were determined by several methods. These methods included: determining dissociation constants by observing the absorbance at 502 nm of a ternary complex of the enzyme, glycine, and the folate compounds; determining inhibition constants from steady-state reactions; and determining the rate of formation and breakdown of the enzyme inhibitor complex by rapid reaction kinetics. Studies of the dissociation and inhibitor constants showed that both 5-methyltetrahydrofolate and 5-formyltetrahydrofolate have essentially the same affinity for the enzyme-glycine binary complex. However, rapid reaction and steady-state kinetic studies showed that the triglutamate form of 5-formyltetrahydrofolate both binds and is released much more slowly from the enzyme-glycine binary complex, compared with the triglutamate form of 5-methyltetrahydrofolate. The results also showed that only one rotamer of 5-formyltetrahydrofolate binds at the active site of serine hydroxymethyltransferase. The results are discussed in terms of the possible role of 5-formyltetrahydrofolate polyglutamates in regulation of one-carbon metabolism. |
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| Keywords |
Animals; Circular Dichroism; Cytosol/enzymology; Escherichia coli/enzymology; Glycine/metabolism; Glycine Hydroxymethyltransferase/antagonists & inhibitors; Glycine Hydroxymethyltransferase/metabolism; Kinetics; Mitochondria/enzymology; Molecular Structure; Protein Binding; Pteroylpolyglutamic Acids/metabolism; Pteroylpolyglutamic Acids/pharmacology; Rabbits; Structure-Activity Relationship |
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